1. 直接写出得数。
$96÷24=$ $40÷20=$ $1.4+1.3=$
$3.7+2.6=$ $7.6-3.9=$ $6.54+5.9=$
$30×23=$ $12×8=$ $2.7-1.28=$
$5-2.7=$ $450÷15=$ $7.3+1.82=$
$12-6.52=$ $2.6-1.91=$ $100-89.7=$

$96÷24=4$
$40÷20=2$
$1.4+1.3=2.7$
$3.7+2.6=6.3$
$7.6-3.9=3.7$
$6.54+5.9=12.44$
$30×23=690$
$12×8=96$
$2.7-1.28=1.42$
$5-2.7=2.3$
$450÷15=30$
$7.3+1.82=9.12$
$12-6.52=5.48$
$2.6-1.91=0.69$
$100-89.7=10.3$

2. 算一算，比一比。
$3.4-2.8=$ $0.2+0.8=$ $0.6+5.8=$
$3.4-2.8+5.8=$ $5.25-(0.2+0.8)=$ $3.4+2.8+5.8=$

$3.4-2.8=0.6$
$0.2+0.8=1$
$0.6+5.8=6.4$
$3.4-2.8+5.8$
$=0.6+5.8$
$=6.4$
$5.25-(0.2+0.8)$
$=5.25-1$
$=4.25$
$3.4+2.8+5.8$
$=6.2+5.8$
$=12$

3. 计算下列各题，能简算的要简算。
$13.9-1.7-3.3$ $45.18+7.09+4.82$
$67.39-(17.39+3.5)$ $21.38+3.67+8.62+6.33$
$9.56+78.4-2.99$ $7.23+19.03+8.77$

$13.9-1.7-3.3$
$=13.9-(1.7+3.3)$
$=13.9-5$
$=8.9$
$45.18+7.09+4.82$
$=45.18+4.82+7.09$
$=50+7.09$
$=57.09$
$67.39-(17.39+3.5)$
$=67.39-17.39-3.5$
$=50-3.5$
$=46.5$
$21.38+3.67+8.62+6.33$
$=(21.38+8.62)+(3.67+6.33)$
$=30+10$
$=40$
$9.56+78.4-2.99$
$=87.96-2.99$
$=84.97$
$7.23+19.03+8.77$
$=7.23+8.77+19.03$
$=16+19.03$
$=35.03$

4. 把下面的分数改写成小数再计算。
$\frac{1}{10}+\frac{4}{10}$ $\frac{93}{100}-\frac{76}{100}$ $\frac{3}{100}+\frac{5}{10}$ $\frac{7}{10}-\frac{61}{100}$

$\frac{1}{10}+\frac{4}{10}=0.1+0.4=0.5$
$\frac{93}{100}-\frac{76}{100}=0.93-0.76=0.17$
$\frac{3}{100}+\frac{5}{10}=0.03+0.5=0.53$
$\frac{7}{10}-\frac{61}{100}=0.7-0.61=0.09$